The body temperature of mammals is normally tightly controlled by an autonomic regulatory system referred to herein as the thermoregulatory system. A primary effector of this regulatory system is blood flow to specialized skin areas where heat from the body core may be dissipated to the environment. Normally, when body and/or environmental temperatures are high, the dilation of certain blood vessels favors high blood flow to these skin areas, and as environmental and/or body temperatures fall, vasoconstriction reduces blood flow to these skin areas and minimizes heat loss to the environment.
Strategic inducement of vasodilation and heat transfer in targeted portions of the body, such as the extremities, may exert positive therapeutic benefits in remote regions of the body. For example, manipulating heat transfer across the skin may change the core temperature of the mammalian body in response. Unfortunately, it may be difficult to induce such changes to an extent sufficient for therapy, given the human body's refined ability to thermoregulate to maintain temperature homeostasis or normothermia.
By applying heat and subatmospheric (negative) pressure to a hypothermic individual's skin, normothermia may be achieved (see, e.g., Grahn et al., “Recovery from mild hypothermia can be accelerated by mechanically distending blood vessels in the hand,” J. Appl Physiol. (1998) 85(5):1643-8). Other therapeutic applications for cooling the skin to achieve normothermia have also been described; e.g., in treating cancer as described in U.S. Pat. No. 7,182,776 to Grahn. However, therapeutic applications for continuously applying heat to the skin while at normothermia to increase microvascular circulation and/or to adjust blood viscosity have not been demonstrated.
Every year, millions of dollars are spent on treatments and drugs for reducing blood viscosity. Such drugs suffer from a variety of drawbacks including cost and side effects such as dizziness, headache, nausea, vomiting, chest pain, and irregular heartbeat.
In view of the foregoing drawbacks of previously known systems, it would be desirable to provide a robust and economical system to increase whole body circulation and to increase or decrease blood viscosity.